There was recently an interesting article in the New York times with the attention provoking title:

To Save the Planet, Don’t Plant Trees

The article was written by an assistant professor of atmospheric chemistry at Yale.

In the article the author warns of socalled V.O.C.'s, (something I haven't heard of before):

>Worse, trees emit reactive volatile gases that contribute to air pollution and are hazardous to human health. These emissions are crucial to trees — to protect themselves from environmental stresses like sweltering heat and bug infestations. In summer, the eastern United States is the world’s major hot spot for volatile organic compounds (V.O.C.s) from trees.

and moreover they write:

>Climate scientists have calculated the effect of increasing forest cover on surface temperature. Their conclusion is that planting trees in the tropics would lead to cooling, but in colder regions, it would cause warming.

if I understood the article right then more or less both facts taken together (the carbon cycle and its possible wrong understandings is also mentioned) leads to the recommendation: " Don’t Plant Trees." There are no references with respect to the claims though.

even if, as the author writes:

>Planting trees and avoiding deforestation do offer unambiguous benefits to biodiversity and many forms of life. But relying on forestry to slow or reverse global warming is another matter entirely.

If you look at that pretty foto traumawald by Christian Miersch, who
had recently commented here on Azimuth, then it seems indeed to be an important question wether science is able to determine the right measures to adress climate change.

For me this article brought however up some question, which I've been tossing around for quite a while, which is the question of the role of certain thermodynamic quantities like entropy and chemical energy in the question of global warming. That is a dark surface absorbs a lot of infrared (thats what I figure is behind the assertion: planting trees in the colder regions would lead to cooling etc. that is the net albedo change in reversing grasslands and other soils into forests seems to be different in differetn climates, where I am not sure wether I understood all the resonings behind this)) but one question is also: what's happening with the absorbed infrared. That is black body radiation is only a fist approximation and it might be worthwhile to think about effects like conversion into chemical energy etc. Like if I would look at this example of upconversion then the upconverted light of a dark looking leave would differently contribute to the overall radiation and in particular to the infrared balance, which plays an important role in the green house effect. In that context I am also asking myself how big are the cooling effects of human efforts in killing biodiversity and building rigid structures like streets and houses. That is exageratedly speaking: if earth would be covered with concrete then this could be seen as lowering the overall earth entropy, and if this would be the case some of the sun's energy would have needed to go into that entropy lowering and not into heat. I was hesitating to ask this question, because I always had some unease with certain thermodynamical laws (visible e.g. here.), but I am not sure how much of this under-understanding is due to missing out some literature or forgetting learned content.